Pathogens, particularly bacterial microorganisms, in contaminated water are the leading cause of poor health and disease worldwide. Poor quality drinking water has emerged as a major health concern in all parts of the world, particularly in developing nations. The pathogens or microbial organisms responsible for this problem are generally classified by their sizes. Protozoa are relatively large pathogens, in the range of 1-300 microns, and include cryptosporidia and giardia. Bacteria are smaller, typically in the range of 0.1-10 microns, and include salmonella and E. coli. Viruses are the smallest pathogens, and the most difficult to deactivate, and are typically in the size range of 0.005 to 0.1 microns.
The diseases caused by these microorganisms have symptomatic origins including fevers, diarrhea, and jaundice; while treatable, if left unchecked can develop into serious diseases and possibly death. According to statistics reported by the World Health Organization (www.who.org), water contaminated with harmful bacteria causes the death of about five (5) million humans annually, the majority of whom are children under five years of age.
In developed countries, municipal water systems regularly break down, leaving bacterial contaminants and other pathogens including viruses and parasites in the drinking water. In developing countries, water has become increasingly scarce, and with high density populations, there is often little to no provision for treating water intended for human consumption. It is estimated that over 1.5 billion people lack access to safe drinking water.